Analysis of weight on bit on torsional stick/slip vibration of drill string

Ali Makvandi¹

1) Iran-University of

Publication : 2nd. International Congress on science & Engineering - paris(parisconf.com)
Abstract :
The slip/slip vibration phenomenon is an example of deleterious drilling operations. Field experiments show that this phenomenon occurs when a heavy weight is applied to the drill. In this paper, the effect of weight on bit on slip/slip vibration is studied. The drilling motion equations are considered based on the pendulum model. Based on the field parameters of the drill motion and the stick/slip vibration are discussed. Negative damping effect occurs during the stick to slip phase vibration. As the weight of bit increases, the drill behavior changes from steady to stick/slip vibration, thus the weight on bit reaches a critical value. The stick/slip vibration is reflected in the oscillatory motion of the bit as it passes from phase to other phase. Without stick/slip vibration mode, the drill bit vibrates as a damping and eventually continues to move in the same manner.
Keywords : Torsional vibration stick/slip vibration drill bit vibration drilling